Cerebrospinal fluid lactate in the diagnosis of meningitis. Diagnostic value compared to standard biochemical methods.

Cerebrospinal fluid (CSF) lactate was determined in 245 patients by means of a rapid enzymatic method (Monotest Lactate). The mean value was 1.61 mmol/l (range 0.79-3.33) in 104 control patients, 2.06 mmol/l (range 0.76-4.31) in 121 patients with aseptic meningitis, and 8.18 mmol/l (range 1.77-19.21) in 20 patients with bacterial meningitis. In most of the patients CSF protein and the CSF/blood glucose quotient were also determined. Lactate and glucose quotient differentiated equally well between aseptic and bacterial meningitis while protein was somewhat less useful. Suitable values for discrimination between aseptic and bacterial meningitis were judged to be 3.0 mmol/l for CSF lactate, 1.0 g/l for CSF protein and 0.5 for the glucose quotient. Combinations of tests improved the diagnostic accuracy in aseptic but not in bacterial meningitis. In 2 patients with bacterial meningitis all tests failed. CSF lactate may be used as a supplementary aid in the diagnosis of meningitis. Its diagnostic efficacy was equal to but not better than that of the traditional methods.